Elsevier

Heart Rhythm

Volume 20, Issue 7, July 2023, Pages 970-975
Heart Rhythm

Clinical
Sudden Death
Causes and clinical consequences of inappropriate shocks experienced by patients wearing a cardioverter-defibrillator

https://doi.org/10.1016/j.hrthm.2023.03.1604Get rights and content

Background

The LifeVest® wearable cardioverter-defibrillator (WCD) prevents sudden cardiac death in at-risk patients who are not candidates for an implantable defibrillator. The safety and efficacy of the WCD may be impacted by inappropriate shocks (IAS).

Objective

The purpose of this study was to assess the causes and clinical consequences of WCD IAS in survivors of IAS events.

Methods

The Food and Drug Administration’s Manufacturers and User Facility Device Experience database was searched for IAS adverse events (AE) that were reported during 2021 and 2022.

Results

A total of 2568 IAS-AE were found (average number of IAS per event: 1.5 ± 1.9; range 1–48). IAS were caused by tachycardias (1255 [48.9%]), motion artifacts (840 [32.7%]), and oversensing (OS) of low-level electrical signals (473 [18.4%]) (P <.001). Tachycardias included atrial fibrillation (AF) (828 [32.2%]), supraventricular tachycardia (SVT) (333 [13.0%]), and nonsustained ventricular tachycardia/fibrillation (NSVT/VF) (87 [3.4%]). Activities responsible for motion-induced IAS included riding a motorcycle, lawnmower, or tractor (n = 128). In 19 patients, IAS induced sustained ventricular tachycardia or ventricular fibrillation that subsequently were terminated by appropriate WCD shocks. Thirty patients fell and suffered physical injuries. Conscious patients (n = 1905) did not use the response buttons to abort shocks (47.9%) or used them improperly (20.2%). IAS resulted in 1190 emergency room visits or hospitalizations, and 17.3% of patients (421/2440) discontinued the WCD after experiencing IAS, especially multiple IAS.

Conclusions

The LifeVest WCD may deliver IAS caused by AF, SVT, NSVT/VF, motion artifacts, and oversensing of electrical signals. These shocks may be arrhythmogenic, result in injuries, precipitate WCD discontinuation, and consume medical resources. Improved WCD sensing, rhythm discrimination, and methods to abort IAS are needed.

Introduction

The wearable cardioverter-defibrillator (WCD) prevents sudden cardiac death in at-risk patients who are not candidates for an implantable defibrillator.1, 2, 3, 4, 5, 6, 7 As suggested by VEST (Vest Prevention of Early Sudden Death Trial),3 the efficacy of the WCS in clinical practice may be significantly impacted by patient noncompliance caused by inappropriate shocks (IAS), frequent false alarms, and device discomfort. WCD IAS may induce ventricular fibrillation (VF) or ventricular tachycardia (VT) or cause asystolic cardiac arrest,4,8 and they often result in an emergency room visit or hospitalization. Importantly, IAS may precipitate WCD discontinuation by the patient or provider.

The LifeVest® (ZOLL Medical Corp, Pittsburgh, PA) was introduced in 2001, and the current LifeVest 4000 WCD has been available since 2009. In a previous study, we described deaths caused by postshock asystole following WCD IAS.8 The purpose of this study was to assess IAS in ambulatory patients who survived IAS delivered by the LifeVest WCD and were reported to the Food and Drug Administration (FDA) during 2021 and 2022.

Section snippets

Methods

The Allina Institutional Review Board determined that this study did not constitute human subjects research because it utilized a publicly available database that only includes de-identified data.

Results

During 2021 and 2022, the FDA received 2568 adverse event reports from the manufacturer, describing 3929 IAS (average IAS per event: 1.5 ± 1.9; range 1–48) delivered by the LifeVest WCD 4000 that were experienced by nonhospitalized patients. All except 9 events occurred in the United States. Of the 2071 IAS events during which the patient's mental status was known, 1909 patients (92.3%) were conscious, 106 (5.1%) were unconscious, 52 (2.5%) were sleeping, and 4 (0.2%) appeared confused.

Discussion

The results of this study suggest that LifeVest WCD IAS are caused equally by AF/RVR, SVT, or NSVT and signals generated by motion or oversensing of low-level electrical artifacts. The incidence of these IAS is not known, but 2568 individual IAS events were reported by the manufacturer to the FDA during 2021 and 2022. In addition to the pain and discomfort of high-voltage shocks, we found IAS could be arrhythmogenic and result in physical injuries. Perhaps most importantly, IAS caused 17% of

Conclusion

The LifeVest wearable cardioverter-defibrillator may deliver IAS caused by AF, SVT, NSVT/VF, motion artifacts, and oversensing of low-level electrical signals. These shocks can be arrhythmogenic, result in physical injuries, precipitate discontinuation of the WCD, and consume expensive medical resources. Improved WCD sensing technology, rhythm discrimination, and methods to abort IAS are needed.

Acknowledgment

We are grateful to the Joseph F. Novogratz family for its support of this research through the Heart Rhythm Science Center of the Minneapolis heart Institute Foundation.

References (19)

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Cited by (1)

Funding Sources: Minneapolis Heart Institute Foundation, Minneapolis, Minnesota.

Disclosures: The authors have no conflicts of interest to disclose.

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